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17 Jun 2002
Force detection with Atto-Newton precision has been achieved by an IBM-Stanford team of physicists led by Daniel Rugar at IBM. This work, reported at last week'sAPS meeting in Kansas City, was carried out with a magnetic resonance force microscope (MRFM), a device that combines nuclear magnetic resonance technologywith probe microscope technology. The goal is nothing less than the ability to make 3-dimensional, non-destructive, in-situ atomic-resolution images of atoms,molecules, defects in solids, dopants in semiconductors, and binding sites in viruses.
In the IBM-Stanford setup, a thin silicon cantilever, 230 microns long but only 60 nm thick, is poised above a tiny sample. A magnetic particle mounted on thecantilever interacts (under the additional influence of fields from an RF coil) with tiny volumes of magnetic atoms in the sample.
Under the right circumstances the particle on the cantilever will begin to resonantly oscillate; the cantilever's movement shifts a laser interference pattern viewedthrough an optical fiber. In this way Rugar can measure tiny magnetic interaction with a resolution of 7 x 10^-18 Newtons, the most sensitive force measurement evermade with a probe microscope. With further refinement the MRFM process will detect single spins; Rugar hopes to map the spins of electrons in dispersed defectsites in silica.
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